1. Field of the Invention
The present invention relates to a substrate transfer apparatus used to support and transfer a substrate in, e.g., a substrate processing apparatus for performing predetermined processing on the surface of the substrate.
2. Description of the Related Art
When performing processing such as film formation or etching while a substrate is transferred in a vacuum environment, a rack and pinion mechanism, roller driving mechanism, chain driving mechanism, or the like is conventionally used as a substrate transfer apparatus in many cases. Also, Japanese Patent Laid-Open No. 2002-68476 has disclosed a transfer apparatus using a magnetic force.
FIGS. 9A and 9B are views exemplarily showing an example of the arrangement of the main components of the transfer apparatus using a magnetic force. FIG. 9A is a B-B′ sectional view of FIG. 9B. FIG. 9B is an A-A′ sectional view of FIG. 9A. Note that some members such as a vacuum chamber are not illustrated for convenience.
In the arrangement shown in FIGS. 9A and 9B, a carrier 6 holds a substrate 5 upright so that the major surface is parallel to the vertical direction. The transfer apparatus horizontally transfers the carrier 6 parallel to the major surface of the substrate 5. The carrier 6 has a guide rail portion 13 having a rectangular or curved groove 13a. A carrier supporting means 21 fixed to a vacuum chamber (not shown) has a plurality of guide rollers 22. In this arrangement, the guide rollers 22 are fitted in the groove 13a of the guide rail portion 13, and the carrier 6 horizontally moves on the rotating guide rollers 22.
In the example shown in FIGS. 9A and 9B, the transfer apparatus has a magnet group 17 as a means for transferring the carrier 6. The magnet group 17 is formed by alternately arranging S- and N-pole magnets in the transfer direction at the lower end of the carrier 6. A magnetic screw 27 is set in the vacuum chamber with a predetermined spacing from the magnet group 17. The central axis of the magnetic screw 27 is parallel to the transfer direction of the carrier 6. A double-spiral magnetic coupling portion including S- and N-pole spiral portions formed at the same pitch as that of the S- and N-pole magnets of the magnet group 17 is formed on the surface of the magnetic screw 27. When the magnetic screw 27 is rotated, the S- and N-pole spiral portions move in a portion corresponding to the magnet group 17 relative to the transfer direction of the carrier 6. Consequently, the carrier 6 is transferred in the direction of an arrow C by the attractive force between the S- and N-pole spiral portions and the N- and S-pole magnets of the magnet group 17.
In this conventional transfer apparatus as exemplarily shown in FIGS. 9A and 9B, particles are generated by the friction between the surface of the groove 13a of the guide rail portion 13 of the carrier 6 and the guide rollers 22 of the carrier supporting means 21. Contamination of the substrate 5 by the particles is a cause of a defective product. Also, the friction between the groove 13a and guide rollers 22 wears the guide rail portion 13 and guide rollers 22 and changes the height of the carrier 6. This makes it necessary to periodically perform maintenance to adjust the height of the carrier 6 and replace worn parts.